US-led coalition forces have clashed with insurgents across Iraq in escalating violence.
Militias loyal to Moqtada Sadr pose a dilemma for the US
US marines have seized part of the flashpoint town of Falluja, a centre of Sunni Muslim resistance, after more than a day of fighting.
There has also been further violence in Shia areas, as coalition forces battle militias loyal to radical cleric Moqtada Sadr for a third day.
Mr Sadr remains surrounded by armed supporters in the holy city of Najaf.
His militia, known as the Mehdi Army, has staged violent demonstrations and attacked US-led forces in several Iraqi cities.
In Tuesday's fighting across Iraq:
- There were heavy clashes in Falluja, where US marines, backed by helicopter gunships, tanks and assault vehicles, seized part of the town; a number of Iraqis were reported killed
- Italian troops killed 15 Iraqis in clashes with Shia militants in the southern city of Nasiriya
- One Ukrainian soldier was killed and five wounded in clashes with militants in Kut, south of Baghdad, the Ukrainian defence ministry said
- A Bulgarian truck driver was killed when his convoy came under attack near Nasiriya
- Two Polish and three Bulgarian soldiers were wounded in a shootout near the city of Karbala, a Polish military spokesman said
- Clashes were reported in the southern town of Amara, where UK troops are responsible for security;
fighting there has left 12 Iraqis dead over the past 48 hours.
Amid the increasing insecurity, Iran has warned its nationals not to travel to neighbouring Iraq, even for brief pilgrimages to Shia Muslim holy sites, Iranian state media reported.
More than 50 people have been killed in two days of protests by Mr Sadr's supporters.
The unrest was triggered by the closure of Mr Sadr's al-Hawza newspaper a week ago on the grounds that it was inciting violence.
A statement by the cleric, quoted by Reuters news agency, said: "This insurrection shows that the Iraqi people are not satisfied with the occupation and they will not accept oppression."
US Defence Secretary Donald Rumsfeld said there were no plans to send additional troops to Iraq.
He told a news conference there were about 135,000 US troops in Iraq.
This was an increase from previous levels of about 115,000, because a massive changeover of forces was taking place, but the number was set to go down again, he said.
Mr Rumsfeld said US commanders had not asked for reinforcements: "At the present time they have not requested a change in their plan."
The BBC's Nick Childs at the Pentagon says the timing and the nature of the latest violence may make it the most serious potential threat to the US-led coalition in Iraq for nearly a year.
He says US commanders face a series of dilemmas, but their priority is how and when to deal with Mr Sadr.
A warrant has been issued for Mr Sadr's arrest in connection with the killing of a rival cleric, Abdel-Majid al-Khoei, in Najaf in April 2003.
One of Mr Sadr's top aides, Mustafa Yacoubi, has already been arrested in connection with the murder, but the cleric denies involvement.
Our correspondent says US forces want to be seen to be decisive in acting against Mr Sadr, but do not want to provoke a backlash.
The US has said it is considering sending additional troops to Iraq.